3. Selected patients with undefined illnesses who may have weakness, myalgias, or an elevated CK may be evaluated to establish a diagnosis and, if they are found to have IIM, would be offered the opportunity to enter the study. Such patients would undergo history and physical examination, blood tests when clinically indicated (incl 20 cc for research purposes), and other procedures as clinically indicated, including an MRI examination to establish an optimal site for muscle biopsy.